“Oh, the depth of the riches and wisdom and knowledge of God!” Paul exclaims in today’s Epistle. Today’s Psalm, too, takes up the triumphant note of joy and thanksgiving. Why? Because in the Gospel, the heavenly Father reveals the mystery of His kingdom to Peter.

With Peter, we rejoice that Jesus is the anointed son promised to David, the one prophesied to build God’s temple and reign over an everlasting kingdom (see 2 Samuel 7).

What Jesus calls “my Church” is the kingdom promised to David’s son(see Isaiah 9:1-7). As we hear in today’s First Reading, Isaiah foretold that the keys to David’s kingdom would be given to a new master, who would rule as father to God’s people.

Jesus, the root and offspring of David, alone holds the kingdom’s keys (see Revelation 1:18; 3:7; 22:16). In giving those keys to Peter, Jesus fulfills that prophecy, establishing Peter - and all who succeed him - as holy father of His Church.

His Church, too, is the new house of God - the spiritual temple founded on the “rock” of Peter, and built up out of the living stones of individual believers (see 1 Peter 2:5).

Abraham was called “the rock” from which the children of Israel were hewn (see Isaiah 51:1-2). And Peter becomes the rock from which God raises up new children of God (see Matthew 3:9).

The word Jesus uses - “church” (ekklesia in Greek) - was used in the Greek translation of the Old Testament for the “assembly” of God’s children after the exodus (see Deuteronomy 18:16; 31:30).

His Church is the “assembly of the firstborn” (see Hebrews 12:23; Exodus 4:23-24), established by Jesus’ exodus (see Luke 9:31). Like the Israelites, we are baptized in water, led by the Rock, and fed with spiritual food (see 1 Corinthians 10:1-5).

Gathered at His altar, in the presence of angels, we sing His praise and give thanks to His holy name.